We need to know that an emperor's tomb is not as easy to understand thoroughly as we thought, and we don't know some things at that time for a long time, which has caused us a lot of difficulties. After all, it is very difficult for us to study an imperial tomb without relevant data and information, and we are not very good at archaeological work, so there will be many times when we can't study what we want well, which is very common.
Because it is an ancient imperial tomb after all, and in that time when people believed in gods, people definitely liked to be buried in places with good geomantic omen. Plus, it is the emperor's mausoleum, so the defense work must be arranged very properly, and some things in the mausoleum are incomprehensible, so even if we can find a mausoleum to enter, we don't know anything about the written language and cultural customs at that time.
and it's been a long time now, and some things in the imperial tombs built by Emperor Jianwen at that time are very difficult for us to understand, because some emperors like some rare treasures, and some even make their tombs very special, so it's a great difficulty for our archaeological work. After all, we don't have relevant information and knowledge, so we haven't studied anything for ten years.
That means we don't know the emperors in ancient times, because they all lived a long time ago, so it is difficult for us to understand them.